1. Field of the Invention
The present invention relates to a stereoscopic image processing apparatus for a vehicular distance detecting system and more particularly to a stereoscopic image processing apparatus capable of arbitrarily combining for use an image detecting unit and an image processing unit.
2. Prior Arts
Modern advanced safety vehicles are equipped with a distance detecting means for detecting a distance between the self vehicle and other vehicles, obstacles and surrounding objects. Such a distance detecting means comprises an image detecting unit for taking picture images of solid objects, lane markers and the like and for outputting image signals and an image processing unit for processing those image signals into distance information.
A typical example of the image detecting unit employs optical systems, i.e., a pair of left and right hands cameras disposed in a horizontally aligned relation at a prescribed distance apart from each other.
The image processing unit successively shifts the image signals from the image detecting unit and electrically superimposes them one over the other to find a best match of two images from the left and right hands cameras, so that the distance from those cameras to an object is calculated based on the principle of triangulation.
Therefore, it is desirable that there is no difference except parallax between two image detecting systems in optical and electrical characteristics. That is to say, optical axes of two cameras must be in parallel with each other and focal lengths must be identical. Further, the difference in aberration characteristic of lenses and the deviation amount at the infinite-point also must be identical. Further, the sensitivity of image elements and the characteristic of signal processing circuits of respective cameras must be identical.
Similarly, on the image processing unit side, the amplitude characteristics such as gain, offset and the like of respective amplifiers must be identical.
The dispersion of the optical characteristics and that of the signal characteristics in both image detecting systems can be adjusted to some extent on the image detecting unit side and on the image processing unit side respectively, however the adjustment is still inadequate. Therefore, in addition to this adjustment, a look-up table correction in which the correction is made based on a table of the sensitivity of image elements, a shading correction in which the sensitivity is corrected per zone of picture images and the like, are used. That is, in the conventional manufacturing process, the image detecting unit is adjusted integrally with the image processing unit to equalize characteristics.
Hence, it is impossible to combine the image detecting unit and the image processing unit each of which is manufactured independently and this inhibits an improvement in productivity. Furthermore, on repairing in markets, when one of these units must be repaired, the other also must be adjusted. In some case, the look-up table of the image processing unit must be reestablished.
The present invention is intended to obviate the aforementioned problems of the known stereoscopic image processing apparatus. An object of the present invention is to provide an improved stereoscopic image processing apparatus whose image detecting unit can be arbitrarily combined for use with the image processing unit.
To attain the object, according to the present invention, the stereoscopic image processing apparatus comprises a first non-volatile memory provided in an image detecting unit for memorizing a camera characteristic data for correcting dispersions of characteristics between a pair of cameras, a means provided in the image detecting unit for reading out the camera characteristic data from the non-volatile memory and for transmitting the data to the image processing unit, a second non-volatile memory provided in an image processing unit for memorizing a circuit characteristic data for correcting dispersions of characteristics between two circuits of the cameras and a means provided in the image processing unit for correcting image signals outputted from the pair of cameras based on the circuit characteristic data read out from the second non-volatile memory and the camera characteristic data sent from the image detecting unit.